On Tue, Mar 6, 2012 at 1:22 PM, John Clements <clements at brinckerhoff.org> wrote:
>> On Mar 5, 2012, at 1:17 PM, Danny Yoo wrote:
>>> Here's another example that's starting to work, though it isn't flashy yet.
>>>>http://hashcollision.org/tmp/js-get-message/js-get-message-parent.html>> Can you be more explicit about what's cool here? I have a sense that it has to do with JS interacting with compiled racket, and I agree that that's very cool, but I could use a bit more hand-holding :).
Yes; of course. I'm sorry, I get so caught up sometimes!
The example is demonstrating JS interacting with Racket, particularly
to interact between JS and World programs. I will be making the world
APIs in Whalesong extensible, so that the set of handlers like on-key,
on-tick, ... etc can be extended by library developers. The key point
is that I don't (and can't) know all event types out there in the
browser. With the appropriate FFI, I should allow library developers
to add in `on-tilt`, `on-touch`, or any of the other events that the
browser is providing, and without needing to touch the core of the
world implementation.
This means I can (and probably should) factor out behavior that used
to be hardcoded in my world implementation (like on-key and on-mouse)
and push these into libraries. As a demonstration, I'm doing this in
the context of my web-world library, with an example that listens on
the `postMessage` event.
The FFI I'm coding for Whalesong will let me connect to JavaScript
APIs in two ways: (1) in the world event-driven style, (2) in
synchronous style. I already had a few of these done by hand. The
FFI mechanism should make it easier for library developers too.
For example, `sleep` looks like:
(define raw-sleep
(js-async-function->procedure
"function(success, fail, n) { setTimeout(success, n); }"))
(define (sleep n)
(unless (real? n)
(raise-type-error 'sleep "real" n))
(void (raw-sleep (inexact->exact (floor (* n 1000)))))
;;;
(displayln "hello")
(sleep 5)
(displayln "world")
So basically, I'm trying to get Whalesong and JS to interact with each
other more nicely. This all just started working a day ago, so I got
excited. :)